In its final form, Newton's Optics closes its third book with 31 queries. The last one - the most extensive - is intended, among other things, to picture a universe submited to several forces. In this way, the success achieved by introducing a force acting at distance between material bodies such as universal gravitation was projected to be extended to the general set of phenomena delimited by natural philosophy. It is argued that the difficulty of this enterprise is justified by the premature condition shared by the new experimental or Baconian sciences that, unlike Principia's dynamics, would resist a rapid mathematical formalism following the Newtonian style. This is: the mediation of a force acting at distance as the key for the general synthesis of natural phenomena. A glance at Newton's query 31 allows us to follow him in his intention to investigate and to install an unifying program of the possible forces of nature.